A new approach for static voltage stability assessment in transmission networks in the presence of OLTC.

• A new comprehensive voltage stability index that characterized by minimal assumptions is formulated and suggested. • Develop a proposed index based on the most accurate transmission line model that can consider the impact of line length on voltage stability evaluation. • The new index takes into account the impact of off-load and on-load tap changer transformers that verified its accuracy by implementing some cases. Recently, voltage stability has become increasingly important because of the expansion and growing demands on power transmission networks. Several factors may contribute to the blackouts occurrence in power system, including severe voltage instability and insufficient power transfer capabilities. To avert voltage collapse in power grids, identifying the critical operating conditions with high precision is crucial. By representing a new index in this paper, the assessment of voltage stability within transmission networks can be undertaken. In contrast to other indices, the proposed index has least assumptions and can assess the voltage stability in power systems with significant precision. Afterward, the suggested index is broadened to encompass the influence of on-load tap changers (OLTC). In order to attain this, the OLTC model has been developed using a precise implementation of mathematical equations, enabling an accurate evaluation of the impact of tap changer variations on voltage stability. To ascertain the efficacy of the proposed index, an evaluation has been conducted on a two-bus as well as 9-and 30-bus transmission test systems under various operational scenarios. The simulation outcomes suggest the superior effectiveness of the suggested index compared to other well-established indices. These results illustrate its ability to accurately assess the impacts of OLTC. [ABSTRACT FROM AUTHOR]